Tailoring energy level and surface basicity of metal oxide semiconductors by rare-earth incorporation for high-performance formaldehyde detection

Formaldehyde is one of the most harmful environmental toxins, which should be less than 60 ppb indoors. Although some sensors, based on metal oxide semiconductors, are fabricated for the detection of formaldehyde, the sensing performance is not satisfactory yet. In this work, some rare earth metals are successfully introduced into In2O3 by a simple electrospinning method. The structure, composition and chemical state of the products are investigated by XRD, TEM, EDS, XPS, TPD and a Kelvin probe. And the sensor based on 5Y-doped In2O3 exhibits the highest response to formaldehyde. Moreover, this sensor also shows an ultra-low detection limit (50 ppb), a short response time (1 s) and good selectivity. It is believed that the improved sensing response and selectivity may originate from the elevated Fermi level and the increased surface basicity of In2O3, leading to the increase of chemisorbed oxygen on the surface and adsorption of formaldehyde.